## 41.2. Checking your Perl Installation

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Before presenting the details of Perl syntax, it would be prudent to check whether or not Perl is on your system and learn how to install it if it isn't. Perl is an interpreted language whose interpreter is called perl. It is this program that reads, compiles and runs Perl source code. Normally, perl will be in your shell's path. It can often be found lurking in /usr/bin or /usr/local/bin. Use your system's find or locate command to track down perl if it doesn't appear in your command path. To see what version of Perl you have, use the `-v` flag like this:

>     $ perl -v

>     This is perl, v5.6.1 built for i686-linux

>     Copyright 1987-2001, Larry Wall

>     Perl may be copied only under the terms of either the Artistic License or the
>     GNU General Public License, which may be found in the Perl 5 source kit.

>     Complete documentation for Perl, including FAQ lists, should be found on
>     this system using `man perl' or `perldoc perl'.  If you have access to the
>     Internet, point your browser at http://www.perl.com/, the Perl Home Page.

This Perl is the latest stable version, 5.6.1. Perl is under very active development and newer versions may soon be available. As with all software projects, there is an unstable, developer's version of Perl that currently is 5.7.3. The version number scheme follows the pattern:

Revision number
  These change only when the language is substantially redefined.
Version number
  Even numbers indicate a stable, production-quality release. Odd numbers should only be used by Perl developers and the curious. Version numbers indicate an important change in the language that may affect scripts written to run under a previous version of Perl. Be sure to check out the perldelta manpage for details.
Subversion level
  This number is better thought of as the patch level for a given version. Only bug fixes will appear with each new patch level release. of perl.

Local configuration information about perl can be obtained with the `-V` flag. A slightly abbreviated version of that command's output appears below.

>     $ perl -V
>     Summary of my perl5 (revision 5.0 version 6 subversion 1) configuration:
>       Platform:
>         osname=linux, osvers=2.4.2-2, archname=i686-linux
>         uname='linux marian 2.4.2-2 #1 sun apr 8 20:41:30 edt 2001 i686 unknown '
>         config_args=''
>         hint=recommended, useposix=true, d_sigaction=define
>         ...

>       Compiler:
>         cc='cc', ccflags ='-fno-strict-aliasing ...'
>         optimize='-O2',
>         cppflags='-fno-strict-aliasing'
>         intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=1234
>         ...

>     Characteristics of this binary (from libperl):
>       Compile-time options: USE_LARGE_FILES
>       Built under linux
>       Compiled at Oct  1 2001 16:15:45
>       @INC:
>         /usr/local/lib/perl5/5.6.1/i686-linux
>         /usr/local/lib/perl5/5.6.1
>         /usr/local/lib/perl5/site_perl/5.6.1/i686-linux
>         /usr/local/lib/perl5/site_perl/5.6.1
>         /usr/local/lib/perl5/site_perl
>         .

The sections followed by ellipses have been truncated. What's important to note here is that the configuration, compiler, and linker options are available (and are used by the perlbug program if you need to file a bug report about Perl). Of more practical use is the section beginning with `@INC`. This lists the directories in which perl will look for library modules, described later in Section 41.11.

-- JJ

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